Thin Film Resistor Integration into Flex-Boards

Transcription

1 Thin Film Resistor Integration into Flex-Boards 7 rd International Workshop Flexible Electronic Systems November 29, 2006, Munich by Dr. Hans Burkard Hightec H MC AG, Lenzburg, Switzerland 1

2 Content HiCoFlex: Process + Properties Integrated NiCr Thin Film Resistors Making Characterisation and Testing Properties Integration into PCB Conclusions + Future prospects 2

3 HiCoFlex Process Fabrication of Multilayer Structure on Rigid Carrier Substrate Assembling, Bonding, Protection, Test Separation of Multilayer from Rigid Substrate Reuse of Carrier HiCoFlex PAD Gold top layer VIA Release layer Rigid Substrate 3

4 HiCoFlex Resolution and Vias 15 µm line / space conductors Laser cut vias 30 µm Electroplated vias 4

5 HiCoFlex 3D-Packaging 4 ICs, 7 x 7 mm, Flip-Chip on HiCoFlex BGA Pitch 1.27 mm Flip-Chip PbSn-Solder Interconnections Pitch 180 µm Side view 5

6 Content HiCoFlex: Process + Properties Integrated NiCr Thin Film Resistors Making Characterisation and Testing Properties Integration into PCB Conclusions + Future prospects 6

7 Making NiCr Resistors in HiCoFlex Making of integrated resistors in HiCoFlex Release layer Polyimide P0 Sputter NiCr, lithography R Sputter Ti/Cu, lithography L1 and electroplate Cu/Ni Annealing (aging NiCr) Laser trimming Polyimide P1 Laser drill vias Sputter Ti/Cu, lithography L2 and electroplate Cu/Ni further layers if needed Separation 7

8 Making NiCr Resistor Foil Elements separation layer Ti/Cu ceramics glass deposition of separation layer contact metal polyimide Separation force-free NiCr+Ti/Cu/Ni resistors + contacts anneal + trim R s polyimide foil elements laser drilled vias 8

9 Integrated NiCr Resistors in HiCoFlex 12 Ω 3500 Ω Test Layout Hi Ω 3500 Ω 350 Ω 50 Ω Laser trim cut 9

10 Tests and Characterisation Measure resistance + Laser trimming Drift during PI curing (380 C peak temp) Measure TCR Temperature life test, 1000h, 125 C Humidity test, 1000h, 85% r.h. / 85 C, 18 VDC Bending test 10

11 2% 0% -2% -4% -6% -8% -10% SHIFT - IST Resistor Drift during PI curing Drift of 50 Ohm/sq NiCr at P1 curing, not annealed Resistor value [Ohm] TCR -18 ± 8 ppm/ C, as on Al2O3 Resistors not yet annealed 11 different R s, mean of 98 pcs each Curing at 380 C peak temperature Drift strongly depended on R values High R s: Low positive drift, only 1% Low R s: High negative drift + large scattering. Influence of the metal contacts! 11

12 Temperature Life Test 0.10% 0.08% 0.06% 0.04% 0.02% 0.00% Mean Abs. Drift Integrated Resistors Time [h] at 125 C Resistors annealed 11 different R s, mean of 54 pcs each Storage at 125 C Drift strongly depended on R values High R s: Low drift, typical < 0.05% Low R s: Higher drift Influence of the metal contacts! 25 Ohm 3500 Ohm 50 Ohm 350 Ohm 50 Ohm 50 Ohm 50 Ohm 350 Ohm 50 Ohm 3500 Ohm 25 Ohm 12

13 Humidity Test Drift Humidity Test / Sub1-Blocks 7-9 with 18 V 4% 3% 2% 1% 0% Resistors annealed 11 different R s, 3 pcs each Storage at 85% r.h. / 85 C 18 VDC applied Drift depended on R values Medium R s: Low drift, typical < 1% Low + high R s: Higher drift Without applied voltage: Similar results -1% Resistance (Ohm)

14 Bending Test Bending of Integrated Resistors 0.8% % r = 1.25 mm 180 Resistor change 0.6% 0.5% 0.4% 0.3% 0.2% 1.0 Resistor length 0.1% 0.0% Resistance [Ohm] Simple bending test: Resistance = R bent R straight (reversible strain gauge effect) NiCr layer at neutral line Change comes from stretching of the foil 3 different R s measured Bending effect is small and somehow dependend on resistor lenght and value 14

15 Content HiCoFlex: Process + Properties Integrated NiCr Thin Film Resistors Making Characterisation and Testing Properties Integration into PCB Conclusions + Future prospects 15

16 Integration into PCB SHIFT: The project Lamination of foils with integrated or embedded components and connection to the wiring of the print has been started, but is not finished. PCB manufacturers have shown that the lamination of a flex foil into a flex or rigid board works. See e.g. SEAG i Board In the centre contacting by through holes Near surface contacting by laser drilled vias pictures by courtesy of SEAG 16

17 Content HiCoFlex: Process + Properties Integrated NiCr Thin Film Resistors Making Characterisation and Testing Properties Integration into PCB Conclusions + Future prospects 17

18 Future prospects + Conclusions Conclusions for NiCr thin film resistors can be integrated into HiCoFlex can be laser trimmed Range: 10 Ω k Ω TCR: -18 ± 8 ppm/ C, same as on Al 2 O 3 Stability at 125 C 1000h: Drift < 0.1% are very stable Humidity tests, 18 VDC, 1000h, typ < 1% Bending tests, radius = 1 mm, typ < 1% Integration into flexible PCB: first versions proven Next steps and future prospects for Integration into rigid or flexible PCB : Thin flexible foils with Resistors, RF structures, integrated capacitors and embedded chips (active components) Limit the use of the expensive high resolution techniques to the areas where it is absolutely necessary 18